In article ,
"Richard Fry" wrote:

"Telamon" wrote
Yes that is true that the fundamental by itself will not produce
harmonics of lower frequency but the fundamental is being modulated by
data so mixed products of variable data transmitted mixing with the
carrier will produce frequency energy above and below the fundamental.
If you have long strings of ones or zeros the mixed frequencies will be
as low as the inverse of the period of low frequency data rates.
____________

The spectrum occupied by a data pulse is dependent on the rise and fall
times of the pulse, not on the pulse duration. If the rise and fall times
are constant, spectral bandwidth also will be constant. Only the
distribution of energy within that spectrum will vary for pulses of
different lengths (half-amplitude durations).

Snip

Yes and that would be the case for NRZ data or non return to zero data.

--
Telamon
Ventura, California

"Telamon" wrote

Yes and that would be the case for NRZ data or
non return to zero data.
___________

Once past the pulse transition, NRZ "data" is nothing but a different value
of DC -- the bandwidth of which is infinitely small.

If NRZ data is amplitude modulated onto a carrier via a DC-coupled
modulator, then the effect is to change the amplitude of the carrier from
one steady-state value to another. The occupied spectrum is infinitely
small for steady-state carriers.

For frequency modulation, DC-coupled NRZ data will change the carrier from
one frequency to another, each of which will be infinitely small during
steady-state conditions.

RF